Apparatus for grinding reflectors



FFlC 1 UNITED- STATES- PA-m APPARATUS FOR GRINDING REFLECTORS George F.Tauclimann, Berkeley, Calif. L Application July 17, 1933, Serial-'No'.680,815 v 2 Glaims- 01. 51-54) This invention relates to the art ofabrading In accordance with this invention, the present and particularlyto the abrasion of glass to form practice of using machine formedheavyc'ast iron spherical surfaces. More particularly, the intools isobviated and other means for securing vention relates to the formationof telescope rethe desired spherical surface are provided. These 5flectors of large diameter, usually upward of include the track 22supported in guides 23 on twenty inches. uprights 24. and extendingacross the disc to be Present practice of grinding a concave surfaceground. Screws 26 provide for vertical adjustfor a large reflectorincludes the rotation of the ment of the track.

. glass blank and the manipulation over the face From the track 22 issuspended a carriage 27 10 of the blank of a heavy tool, usually a castiron comprising suspension members 28 provided with block machined tohave a desired curvature. In rollers 29 adapted to roll upon the controlsurforming a true surface as many as three blocks face of track 22 andconnected together by a of different sizes may be required. This makesgrinding tool support 30. the manufacture of these reflectors expensive;in The grinding tool is rotatably supported in this l5 addition, close,true grinding is not secured. carriage by a disc 31 adapted to rotateupon The present invention obviates many difficulties rollers 32 carriedon downturned cars 33 of the including those involved in the use of theheavy support 30 and a pin 34 adapted to be received cast iron blocksand the possibility of inaccuracy in a bearing formed in said support30. in grinding. In addition, I provide a machine Rollers 32 are placeddirectly under the suspen- 20 which can be readily adapted to thegrinding of sion members 28 to insure that the diameter of any surfaceof a desired spherical contour, and the tool in that direction will bemaintained parthis without any heavy and special machine work. allel tothe track 22. Carried on the disc 31 is It is in general the principalobject of the presthe grinding tool 35. ent invention to provide asimple but accurate The grinding tool is preferably formed of some 25'machine for the grinding of spherical surfaces. material which will wearaway during the grind- Another object of the invention is to provide ingoperation as fast or slightly faster than the for the grinding oftelescope reflectors of large material of the blank, and glass has beenfound diameter in a novel manner. As is well known quite satisfactoryfor this purpose. The efiect of r and appreciated, these are concave andmust be this choice of material is to maintain the entire 3U groundextremely true to avoid aberration of the surface of the tool in contactwith the blank image. The present invention is of particular throughoutthe grinding operation, producing a portent in this field. much moreuniform result. Wear of the tool may The invention possesses numerousother adbe compensated for by adjustment of screws 26 vantageousfeatures and objects, some of which, to maintain the effective radius ofthe grinding "35 together with the foregoing, will be set forth atsurface substantially constant. length in the following, wherein thepreferred The contour of the track is readily arrived at. form of myinvention is disclosed. In forming a track having a circular guide sur-In the drawing accompanying and forming a face, I have taken a bar ofcold rolled steel, in one part thereof, case a flat a quarter of an inchthick, two and one "40 Figure 1 is a side elevation of a machine emhalfinches wide and about three feet in length,

bodying features of my invention. and scribed thereon a segment of acircle. The

Figure 2 is a plan view. radius of this circle is that of the curvaturede- In the preferred form of machines disclosed, sired less the distanceof the track from the sur- I provide a rotatable carrier or turn table 6upon face of the tool. The bar is then sawed along 45 which glass disc 7and its support or mount are this line and the two halves are filedsmooth and carried. Clamps 8 and blocks 9 secure the disc are thenlapped together. The positions of the in a central position on the turntable during two halves are reversed during the lapping so thatrotation. An end thrust bearing 11 and a beara true continuous circularguide surface is secured ing 12 support shaft 13 for rotation in asuitable on each. One half is convex and the other con- 50 frame or basestructure indicated generally as 14. cave, the latter being shown in thedrawing. 5

A gear 15 is carried on the shaft 13 and is driven The grindingoperation is begun, after the mirby gear 16 on counter shaft 17. A motor18 is ror blank and the track have been accurately connected by belt 19to pulley 21 on the counter levelled and the abrasive applied, by movingthe shaft to rotate the carrier table and the glass grinding tool to aposition where its edge slightly 5'5 disc 7 thereon. overlies the centerof the blank. At this time the no surfaces of both the tool and blankare substantially flat. Rotation of the turn table 6 is then commencedand the grinding tool is simultaneously rotated in the oppositedirection by hand. This results in a spherical hollow being ground inthe mirror blank while the grinding tool loses its square edge andassumes a complementary, convex form.

When the hollow of the blank has reached a substantial depth, thegrinding tool is moved back and forth along the track, rotation of boththe tool and blank being continued. This results in an extension of thecentral hollow of the blank toward its edges, until it is finally formedto a concave spherical surface.

It is to be understood that the embodiment disclosed is that at presentpreferred and that variations therein can be made without departing frommy invention as it is defined in the claims.

I claim:

1. In a machine of the class described, a rotatable table having meansfor detachably securing a blank thereto, and means for supporting agrinding tool in cooperative relation with said table comprising a trackconcentric with the surface to be ground, a suspended carrier movablealong said track, a tool rotatably mounted in said carrier, and means atthe front and back of said carrier for preventing dipping of the edgesof said tool as the carrier is moved along said track.

2. In a machine of the class described, a rotatable table having meansfor detachably securing a blank thereto, and means for supporting agrinding tool in cooperative relation with said table comprising a trackconcentric with the surface to be ground, a suspended carrier movablealong said track, a tool rotatably mounted in said carrier, means at thefront and back of said carrier for preventing dipping of the edges ofsaid tool as the carrier is moved along said track, and means foradjusting the height of said track above said table.

GEORGE F. TAUCHMANN.

